/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <assert.h>
#include <limits.h>
#include <stdlib.h>

#include "uv.h"
#include "internal.h"

#define HAVE_CONDVAR_API() (pInitializeConditionVariable != NULL)

static int uv_cond_fallback_init(uv_cond_t* cond);
static void uv_cond_fallback_destroy(uv_cond_t* cond);
static void uv_cond_fallback_signal(uv_cond_t* cond);
static void uv_cond_fallback_broadcast(uv_cond_t* cond);
static void uv_cond_fallback_wait(uv_cond_t* cond, uv_mutex_t* mutex);
static int uv_cond_fallback_timedwait(uv_cond_t* cond,
    uv_mutex_t* mutex, uint64_t timeout);

static int uv_cond_condvar_init(uv_cond_t* cond);
static void uv_cond_condvar_destroy(uv_cond_t* cond);
static void uv_cond_condvar_signal(uv_cond_t* cond);
static void uv_cond_condvar_broadcast(uv_cond_t* cond);
static void uv_cond_condvar_wait(uv_cond_t* cond, uv_mutex_t* mutex);
static int uv_cond_condvar_timedwait(uv_cond_t* cond,
    uv_mutex_t* mutex, uint64_t timeout);

static void uv__once_inner(uv_once_t* guard, void (*callback)(void))
{
    DWORD result;
    HANDLE existing_event, created_event;

    created_event = CreateEvent(NULL, 1, 0, NULL);
    if (created_event == 0) {
        /* Could fail in a low-memory situation? */
        uv_fatal_error(GetLastError(), "CreateEvent");
    }

    existing_event = InterlockedCompareExchangePointer(&guard->event,
        created_event,
        NULL);

    if (existing_event == NULL) {
        /* We won the race */
        callback();

        result = SetEvent(created_event);
        assert(result);
        guard->ran = 1;

    } else {
        /* We lost the race. Destroy the event we created and wait for the */
        /* existing one to become signaled. */
        CloseHandle(created_event);
        result = WaitForSingleObject(existing_event, INFINITE);
        assert(result == WAIT_OBJECT_0);
    }
}

void uv_once(uv_once_t* guard, void (*callback)(void))
{
    /* Fast case - avoid WaitForSingleObject. */
    if (guard->ran) {
        return;
    }

    uv__once_inner(guard, callback);
}

/* Verify that uv_thread_t can be stored in a TLS slot. */
STATIC_ASSERT(sizeof(uv_thread_t) <= sizeof(void*));

static uv_key_t uv__current_thread_key;
static uv_once_t uv__current_thread_init_guard = UV_ONCE_INIT;

static void uv__init_current_thread_key(void)
{
    if (uv_key_create(&uv__current_thread_key))
        abort();
}

struct thread_ctx {
    void (*entry)(void* arg);
    void* arg;
    uv_thread_t self;
};

static UINT __stdcall uv__thread_start(void* arg)
{
    struct thread_ctx* ctx_p;
    struct thread_ctx ctx;

    ctx_p = arg;
    ctx = *ctx_p;
    uv__free(ctx_p);

    uv_once(&uv__current_thread_init_guard, uv__init_current_thread_key);
    uv_key_set(&uv__current_thread_key, (void*)ctx.self);

    ctx.entry(ctx.arg);

    return 0;
}

int uv_thread_create(uv_thread_t* tid, void (*entry)(void* arg), void* arg)
{
    struct thread_ctx* ctx;
    int err;
    HANDLE thread;

    ctx = uv__malloc(sizeof(*ctx));
    if (ctx == NULL)
        return UV_ENOMEM;

    ctx->entry = entry;
    ctx->arg = arg;

    /* Create the thread in suspended state so we have a chance to pass
   * its own creation handle to it */
    thread = (HANDLE)_beginthreadex(NULL,
        0,
        uv__thread_start,
        ctx,
        CREATE_SUSPENDED,
        NULL);
    if (thread == NULL) {
        err = errno;
        uv__free(ctx);
    } else {
        err = 0;
        *tid = thread;
        ctx->self = thread;
        ResumeThread(thread);
    }

    switch (err) {
    case 0:
        return 0;
    case EACCES:
        return UV_EACCES;
    case EAGAIN:
        return UV_EAGAIN;
    case EINVAL:
        return UV_EINVAL;
    }

    return UV_EIO;
}

uv_thread_t uv_thread_self(void)
{
    uv_once(&uv__current_thread_init_guard, uv__init_current_thread_key);
    return (uv_thread_t)uv_key_get(&uv__current_thread_key);
}

int uv_thread_join(uv_thread_t* tid)
{
    if (WaitForSingleObject(*tid, INFINITE))
        return uv_translate_sys_error(GetLastError());
    else {
        CloseHandle(*tid);
        *tid = 0;
        return 0;
    }
}

int uv_thread_equal(const uv_thread_t* t1, const uv_thread_t* t2)
{
    return *t1 == *t2;
}

int uv_mutex_init(uv_mutex_t* mutex)
{
    InitializeCriticalSection(mutex);
    return 0;
}

void uv_mutex_destroy(uv_mutex_t* mutex)
{
    DeleteCriticalSection(mutex);
}

void uv_mutex_lock(uv_mutex_t* mutex)
{
    EnterCriticalSection(mutex);
}

int uv_mutex_trylock(uv_mutex_t* mutex)
{
    if (TryEnterCriticalSection(mutex))
        return 0;
    else
        return UV_EBUSY;
}

void uv_mutex_unlock(uv_mutex_t* mutex)
{
    LeaveCriticalSection(mutex);
}

int uv_rwlock_init(uv_rwlock_t* rwlock)
{
    /* Initialize the semaphore that acts as the write lock. */
    HANDLE handle = CreateSemaphoreW(NULL, 1, 1, NULL);
    if (handle == NULL)
        return uv_translate_sys_error(GetLastError());
    rwlock->state_.write_semaphore_ = handle;

    /* Initialize the critical section protecting the reader count. */
    InitializeCriticalSection(&rwlock->state_.num_readers_lock_);

    /* Initialize the reader count. */
    rwlock->state_.num_readers_ = 0;

    return 0;
}

void uv_rwlock_destroy(uv_rwlock_t* rwlock)
{
    DeleteCriticalSection(&rwlock->state_.num_readers_lock_);
    CloseHandle(rwlock->state_.write_semaphore_);
}

void uv_rwlock_rdlock(uv_rwlock_t* rwlock)
{
    /* Acquire the lock that protects the reader count. */
    EnterCriticalSection(&rwlock->state_.num_readers_lock_);

    /* Increase the reader count, and lock for write if this is the first
   * reader.
   */
    if (++rwlock->state_.num_readers_ == 1) {
        DWORD r = WaitForSingleObject(rwlock->state_.write_semaphore_, INFINITE);
        if (r != WAIT_OBJECT_0)
            uv_fatal_error(GetLastError(), "WaitForSingleObject");
    }

    /* Release the lock that protects the reader count. */
    LeaveCriticalSection(&rwlock->state_.num_readers_lock_);
}

int uv_rwlock_tryrdlock(uv_rwlock_t* rwlock)
{
    int err;

    if (!TryEnterCriticalSection(&rwlock->state_.num_readers_lock_))
        return UV_EBUSY;

    err = 0;

    if (rwlock->state_.num_readers_ == 0) {
        /* Currently there are no other readers, which means that the write lock
     * needs to be acquired.
     */
        DWORD r = WaitForSingleObject(rwlock->state_.write_semaphore_, 0);
        if (r == WAIT_OBJECT_0)
            rwlock->state_.num_readers_++;
        else if (r == WAIT_TIMEOUT)
            err = UV_EBUSY;
        else if (r == WAIT_FAILED)
            uv_fatal_error(GetLastError(), "WaitForSingleObject");

    } else {
        /* The write lock has already been acquired because there are other
     * active readers.
     */
        rwlock->state_.num_readers_++;
    }

    LeaveCriticalSection(&rwlock->state_.num_readers_lock_);
    return err;
}

void uv_rwlock_rdunlock(uv_rwlock_t* rwlock)
{
    EnterCriticalSection(&rwlock->state_.num_readers_lock_);

    if (--rwlock->state_.num_readers_ == 0) {
        if (!ReleaseSemaphore(rwlock->state_.write_semaphore_, 1, NULL))
            uv_fatal_error(GetLastError(), "ReleaseSemaphore");
    }

    LeaveCriticalSection(&rwlock->state_.num_readers_lock_);
}

void uv_rwlock_wrlock(uv_rwlock_t* rwlock)
{
    DWORD r = WaitForSingleObject(rwlock->state_.write_semaphore_, INFINITE);
    if (r != WAIT_OBJECT_0)
        uv_fatal_error(GetLastError(), "WaitForSingleObject");
}

int uv_rwlock_trywrlock(uv_rwlock_t* rwlock)
{
    DWORD r = WaitForSingleObject(rwlock->state_.write_semaphore_, 0);
    if (r == WAIT_OBJECT_0)
        return 0;
    else if (r == WAIT_TIMEOUT)
        return UV_EBUSY;
    else
        uv_fatal_error(GetLastError(), "WaitForSingleObject");
}

void uv_rwlock_wrunlock(uv_rwlock_t* rwlock)
{
    if (!ReleaseSemaphore(rwlock->state_.write_semaphore_, 1, NULL))
        uv_fatal_error(GetLastError(), "ReleaseSemaphore");
}

int uv_sem_init(uv_sem_t* sem, unsigned int value)
{
    *sem = CreateSemaphore(NULL, value, INT_MAX, NULL);
    if (*sem == NULL)
        return uv_translate_sys_error(GetLastError());
    else
        return 0;
}

void uv_sem_destroy(uv_sem_t* sem)
{
    if (!CloseHandle(*sem))
        abort();
}

void uv_sem_post(uv_sem_t* sem)
{
    if (!ReleaseSemaphore(*sem, 1, NULL))
        abort();
}

void uv_sem_wait(uv_sem_t* sem)
{
    if (WaitForSingleObject(*sem, INFINITE) != WAIT_OBJECT_0)
        abort();
}

int uv_sem_trywait(uv_sem_t* sem)
{
    DWORD r = WaitForSingleObject(*sem, 0);

    if (r == WAIT_OBJECT_0)
        return 0;

    if (r == WAIT_TIMEOUT)
        return UV_EAGAIN;

    abort();
    return -1; /* Satisfy the compiler. */
}

/* This condition variable implementation is based on the SetEvent solution
 * (section 3.2) at http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
 * We could not use the SignalObjectAndWait solution (section 3.4) because
 * it want the 2nd argument (type uv_mutex_t) of uv_cond_wait() and
 * uv_cond_timedwait() to be HANDLEs, but we use CRITICAL_SECTIONs.
 */

static int uv_cond_fallback_init(uv_cond_t* cond)
{
    int err;

    /* Initialize the count to 0. */
    cond->fallback.waiters_count = 0;

    InitializeCriticalSection(&cond->fallback.waiters_count_lock);

    /* Create an auto-reset event. */
    cond->fallback.signal_event = CreateEvent(NULL, /* no security */
        FALSE, /* auto-reset event */
        FALSE, /* non-signaled initially */
        NULL); /* unnamed */
    if (!cond->fallback.signal_event) {
        err = GetLastError();
        goto error2;
    }

    /* Create a manual-reset event. */
    cond->fallback.broadcast_event = CreateEvent(NULL, /* no security */
        TRUE, /* manual-reset */
        FALSE, /* non-signaled */
        NULL); /* unnamed */
    if (!cond->fallback.broadcast_event) {
        err = GetLastError();
        goto error;
    }

    return 0;

error:
    CloseHandle(cond->fallback.signal_event);
error2:
    DeleteCriticalSection(&cond->fallback.waiters_count_lock);
    return uv_translate_sys_error(err);
}

static int uv_cond_condvar_init(uv_cond_t* cond)
{
    pInitializeConditionVariable(&cond->cond_var);
    return 0;
}

int uv_cond_init(uv_cond_t* cond)
{
    uv__once_init();

    if (HAVE_CONDVAR_API())
        return uv_cond_condvar_init(cond);
    else
        return uv_cond_fallback_init(cond);
}

static void uv_cond_fallback_destroy(uv_cond_t* cond)
{
    if (!CloseHandle(cond->fallback.broadcast_event))
        abort();
    if (!CloseHandle(cond->fallback.signal_event))
        abort();
    DeleteCriticalSection(&cond->fallback.waiters_count_lock);
}

static void uv_cond_condvar_destroy(uv_cond_t* cond)
{
    /* nothing to do */
}

void uv_cond_destroy(uv_cond_t* cond)
{
    if (HAVE_CONDVAR_API())
        uv_cond_condvar_destroy(cond);
    else
        uv_cond_fallback_destroy(cond);
}

static void uv_cond_fallback_signal(uv_cond_t* cond)
{
    int have_waiters;

    /* Avoid race conditions. */
    EnterCriticalSection(&cond->fallback.waiters_count_lock);
    have_waiters = cond->fallback.waiters_count > 0;
    LeaveCriticalSection(&cond->fallback.waiters_count_lock);

    if (have_waiters)
        SetEvent(cond->fallback.signal_event);
}

static void uv_cond_condvar_signal(uv_cond_t* cond)
{
    pWakeConditionVariable(&cond->cond_var);
}

void uv_cond_signal(uv_cond_t* cond)
{
    if (HAVE_CONDVAR_API())
        uv_cond_condvar_signal(cond);
    else
        uv_cond_fallback_signal(cond);
}

static void uv_cond_fallback_broadcast(uv_cond_t* cond)
{
    int have_waiters;

    /* Avoid race conditions. */
    EnterCriticalSection(&cond->fallback.waiters_count_lock);
    have_waiters = cond->fallback.waiters_count > 0;
    LeaveCriticalSection(&cond->fallback.waiters_count_lock);

    if (have_waiters)
        SetEvent(cond->fallback.broadcast_event);
}

static void uv_cond_condvar_broadcast(uv_cond_t* cond)
{
    pWakeAllConditionVariable(&cond->cond_var);
}

void uv_cond_broadcast(uv_cond_t* cond)
{
    if (HAVE_CONDVAR_API())
        uv_cond_condvar_broadcast(cond);
    else
        uv_cond_fallback_broadcast(cond);
}

static int uv_cond_wait_helper(uv_cond_t* cond, uv_mutex_t* mutex,
    DWORD dwMilliseconds)
{
    DWORD result;
    int last_waiter;
    HANDLE handles[2] = {
        cond->fallback.signal_event,
        cond->fallback.broadcast_event
    };

    /* Avoid race conditions. */
    EnterCriticalSection(&cond->fallback.waiters_count_lock);
    cond->fallback.waiters_count++;
    LeaveCriticalSection(&cond->fallback.waiters_count_lock);

    /* It's ok to release the <mutex> here since Win32 manual-reset events */
    /* maintain state when used with <SetEvent>. This avoids the "lost wakeup" */
    /* bug. */
    uv_mutex_unlock(mutex);

    /* Wait for either event to become signaled due to <uv_cond_signal> being */
    /* called or <uv_cond_broadcast> being called. */
    result = WaitForMultipleObjects(2, handles, FALSE, dwMilliseconds);

    EnterCriticalSection(&cond->fallback.waiters_count_lock);
    cond->fallback.waiters_count--;
    last_waiter = result == WAIT_OBJECT_0 + 1
        && cond->fallback.waiters_count == 0;
    LeaveCriticalSection(&cond->fallback.waiters_count_lock);

    /* Some thread called <pthread_cond_broadcast>. */
    if (last_waiter) {
        /* We're the last waiter to be notified or to stop waiting, so reset the */
        /* the manual-reset event. */
        ResetEvent(cond->fallback.broadcast_event);
    }

    /* Reacquire the <mutex>. */
    uv_mutex_lock(mutex);

    if (result == WAIT_OBJECT_0 || result == WAIT_OBJECT_0 + 1)
        return 0;

    if (result == WAIT_TIMEOUT)
        return UV_ETIMEDOUT;

    abort();
    return -1; /* Satisfy the compiler. */
}

static void uv_cond_fallback_wait(uv_cond_t* cond, uv_mutex_t* mutex)
{
    if (uv_cond_wait_helper(cond, mutex, INFINITE))
        abort();
}

static void uv_cond_condvar_wait(uv_cond_t* cond, uv_mutex_t* mutex)
{
    if (!pSleepConditionVariableCS(&cond->cond_var, mutex, INFINITE))
        abort();
}

void uv_cond_wait(uv_cond_t* cond, uv_mutex_t* mutex)
{
    if (HAVE_CONDVAR_API())
        uv_cond_condvar_wait(cond, mutex);
    else
        uv_cond_fallback_wait(cond, mutex);
}

static int uv_cond_fallback_timedwait(uv_cond_t* cond,
    uv_mutex_t* mutex, uint64_t timeout)
{
    return uv_cond_wait_helper(cond, mutex, (DWORD)(timeout / 1e6));
}

static int uv_cond_condvar_timedwait(uv_cond_t* cond,
    uv_mutex_t* mutex, uint64_t timeout)
{
    if (pSleepConditionVariableCS(&cond->cond_var, mutex, (DWORD)(timeout / 1e6)))
        return 0;
    if (GetLastError() != ERROR_TIMEOUT)
        abort();
    return UV_ETIMEDOUT;
}

int uv_cond_timedwait(uv_cond_t* cond, uv_mutex_t* mutex,
    uint64_t timeout)
{
    if (HAVE_CONDVAR_API())
        return uv_cond_condvar_timedwait(cond, mutex, timeout);
    else
        return uv_cond_fallback_timedwait(cond, mutex, timeout);
}

int uv_barrier_init(uv_barrier_t* barrier, unsigned int count)
{
    int err;

    barrier->n = count;
    barrier->count = 0;

    err = uv_mutex_init(&barrier->mutex);
    if (err)
        return err;

    err = uv_sem_init(&barrier->turnstile1, 0);
    if (err)
        goto error2;

    err = uv_sem_init(&barrier->turnstile2, 1);
    if (err)
        goto error;

    return 0;

error:
    uv_sem_destroy(&barrier->turnstile1);
error2:
    uv_mutex_destroy(&barrier->mutex);
    return err;
}

void uv_barrier_destroy(uv_barrier_t* barrier)
{
    uv_sem_destroy(&barrier->turnstile2);
    uv_sem_destroy(&barrier->turnstile1);
    uv_mutex_destroy(&barrier->mutex);
}

int uv_barrier_wait(uv_barrier_t* barrier)
{
    int serial_thread;

    uv_mutex_lock(&barrier->mutex);
    if (++barrier->count == barrier->n) {
        uv_sem_wait(&barrier->turnstile2);
        uv_sem_post(&barrier->turnstile1);
    }
    uv_mutex_unlock(&barrier->mutex);

    uv_sem_wait(&barrier->turnstile1);
    uv_sem_post(&barrier->turnstile1);

    uv_mutex_lock(&barrier->mutex);
    serial_thread = (--barrier->count == 0);
    if (serial_thread) {
        uv_sem_wait(&barrier->turnstile1);
        uv_sem_post(&barrier->turnstile2);
    }
    uv_mutex_unlock(&barrier->mutex);

    uv_sem_wait(&barrier->turnstile2);
    uv_sem_post(&barrier->turnstile2);
    return serial_thread;
}

int uv_key_create(uv_key_t* key)
{
    key->tls_index = TlsAlloc();
    if (key->tls_index == TLS_OUT_OF_INDEXES)
        return UV_ENOMEM;
    return 0;
}

void uv_key_delete(uv_key_t* key)
{
    if (TlsFree(key->tls_index) == FALSE)
        abort();
    key->tls_index = TLS_OUT_OF_INDEXES;
}

void* uv_key_get(uv_key_t* key)
{
    void* value;

    value = TlsGetValue(key->tls_index);
    if (value == NULL)
        if (GetLastError() != ERROR_SUCCESS)
            abort();

    return value;
}

void uv_key_set(uv_key_t* key, void* value)
{
    if (TlsSetValue(key->tls_index, value) == FALSE)
        abort();
}
